Ice Jam Flooding
A strong, slowing moving frontal boundary will bring multiple hazards to the Finger Lakes over the next 24-hours.
Temperatures in the upper 40s and low 50s, blustery south winds, and rising dewpoints will continue to melt snow today, and at an increasing pace. Latest modeling this morning still shows 2-4 inches of water equivalent locked up in the snowpack over higher elevations.
Rain will also move in from the west during the morning and midday hours. Most areas should see at least some on and off rain showers by the early afternoon, and much of the area may see steady rain.
Most of the rain will be light to moderate at first, though some briefly heavier rain rates will also be possible. The rain will intensify this evening and become heavy through midnight. Many areas will see three-quarters to an inch of rainfall by midnight with locally higher amounts.
Runoff from the snowmelt and rainfall will be high due to the frozen ground. This will all lead to significant rises on area streams and rivers. Even those rivers in lower elevations, where much of the snow has already melted, will see significant snowmelt contributions from upstream, higher elevations.
These factors on their own would cause high water and localize minor flooding, but few significant problems. However, the rising waters will break up the ice, leading to the threat of ice jams. These will especially be possible near bridges, sharp bends, and narrowing channels, which can all be pinch-points that cause the ice to dam.
Flooding from ice jams is extremely unpredictable and can occur in a matter of minutes. Likewise, downstream flooding can rapidly occur if the jam suddenly releases. The fact that the heaviest rain will come at the end of the rain portion of the event, and that this will occur at night, only raises the hazard level.
Those in flood-prone areas, especially those with a history of ice jams, should have an action plan in place and will need to be extra vigilant this afternoon and especially this evening. Motorists are reminded to never drive through floodwaters. The hazards from flooding are exacerbated at night time due to poor visibility and increased difficulty in assessing the present situation.
Low-lying, poor drainage areas away from rivers may also see some minor to slight flooding issues.
Flooding issues may continue into Friday morning due to runoff and continued ice jamming.
Ice and Snow
After the heavy rain tonight, precipitation will decrease in intensity as the cold front moves through. Temperatures will rapidly fall, leading to a period of freezing rain, followed by sleet.
Much of the area will see a glaze of ice in the hours between midnight and dawn. Localized ice amounts up to a tenth of an inch will be possible, mostly in the higher elevations in Wyoming, Livingston, and western Ontario counties. A few tenths of an inch of sleet will fall on top of the ice.
Precipitation will push off to the northeast as it turns over to snow. Much of the precipitation may therefore end before accumulations can take place over the southeastern half of the Finger Lakes.
Further northwest, where the changeover will take place several hours sooner, there will be some minor snow accumulations. Wyoming, Genesee, northern Livingston, Monroe, and Wayne county may see 2-4 inches fall by Friday morning. Accumulations elsewhere will be around an inch or less.
The snow on top of the ice will make for extra slick travel conditions early Friday. Even areas that only see a light coating of snow will still have icy roads until they are treated. Use caution traveling in the morning, especially early on.
Some limited lake effect snow will continue Friday morning, especially over Cayuga, Onondaga, and Cortland counties. This snow may linger as late as the mid afternoon and will put down an inch or two of additional snow.
Wind, Temperatures, and Looking Beyond
Winds during the day today will still be from the south but will not be as strong as yesterday. However, as the front moves in and intensifies tonight, the wind ahead of the front will increase.
The strongest winds, with gusts over 50 mph, are likely to remain southeast of the Finger Lakes, with the only exception being southern Tioga County, where a Wind Advisory is in place. Still, gusts may briefly go over 40 mph from Elmira to Ithaca to Syracuse and for points eastward, with 30-40 mph gusts elsewhere.
Temperatures will remain in the upper 40s and low 50s until the front moves through. Within minutes, temperatures will fall to the mid and low 30s. By dawn Friday, temperatures will settle in the low and mid 20s, where they will remain much of Friday.
Temperatures will dip into the 10s Friday night, only to push back toward 30 degrees Saturday morning with south winds taking hold once more. Another cold front will move through during the afternoon with an inch or two of snow.
Strong winds will develop for Saturday afternoon behind the front. These winds will come in from the west with gusts of 40-50 mph. The strongest winds will be across Wyoming, Genesee, Livingston, Monroe, and western Wayne and Ontario counties.
The weather will then quiet down. Sunday looks sunny, while Monday will just have some thin clouds. Both days will have south winds, pushing highs to the low 40s on Sunday and well into the 50s on Monday.
A weaker system is expected to bring some more rain Tuesday into early Wednesday, but temperatures will remain well above average. Cooler air will work in for the second half of next week and should persist with highs in the 20s and 30s to close out February and begin March.
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This graphic represents an average over the entire Finger Lakes region. Localized variations should be expected.
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